Abstract
The Caesalpinia group is a large pantropical clade of ca. 205 species in subfamily Caesalpinioideae (Leguminosae) in which generic delimitation has been in a state of considerable flux. Here we present new phylogenetic analyses based on five plastid and one nuclear ribosomal marker, with dense taxon sampling including 172 (84%) of the species and representatives of all previously described genera in the Caesalpinia group. These analyses show that the current classification of the Caesalpinia group into 21 genera needs to be revised. Several genera (Poincianella, Erythrostemon, Cenostigma and Caesalpinia sensu Lewis, 2005) are non-monophyletic and several previously unclassified Asian species segregate into clades that merit recognition at generic rank. In addition, the near-completeness of our taxon sampling identifies three species that do not belong in any of the main clades and these are recognised as new monospecific genera. A new generic classification of the Caesalpinia group is presented including a key for the identification of genera, full generic descriptions, illustrations (drawings and photo plates of all genera), and (for most genera) the nomenclatural transfer of species to their correct genus. We recognise 26 genera, with reinstatement of two previously described genera (Biancaea Tod., Denisophytum R. Vig.), re-delimitation and expansion of several others (Moullava, Cenostigma, Libidibia and Erythrostemon), contraction of Caesalpinia s.s. and description of four new ones (Gelrebia, Paubrasilia, Hererolandia and Hultholia), and make 75 new nomenclatural combinations in this new generic system.
Highlights
Resolving generic limits, reconciling genera with monophyletic groups and establishing stable generic classifications remain some of the most active and at times contentious issues in systematics (Humphreys and Linder 2009, Vences et al 2013, Garnock-Jones 2014)
In the maximum parsimony (MP) and Maximum Likelihood (ML) analyses, Lophocarpinia is nested within Haematoxylum, but in the Bayesian analyses Lophocarpinia is sister to Haematoxylum
Whilst several recent studies based on single DNA sequence loci or morphology have partially addressed this problem (Simpson et al 2003, Nores et al 2012, Gagnon et al 2013), the results presented here, based on combined analyses of six DNA sequence loci totaling 8.8 kb of DNA sequence data, and sampling 84% of species, provide the most comprehensively sampled and robust phylogeny of the group to date
Summary
Resolving generic limits, reconciling genera with monophyletic groups and establishing stable generic classifications remain some of the most active and at times contentious issues in systematics (Humphreys and Linder 2009, Vences et al 2013, Garnock-Jones 2014) This is very much the case in the large plant family Leguminosae, where delimitation of genera has been in a state of considerable flux, in large part because of the lack of robust and well-sampled species-level phylogenies (LPWG 2013, and LPWG submitted). [Jobson and Luckow 2007], Monopetalanthus Harms [Wieringa 1999], Hymenostegia Harms [Mackinder et al 2013; Mackinder and Wieringa 2013; Wieringa et al 2013], Vigna Savi [Delgado-Salinas et al 2011], Lonchocarpus Kunth [Da Silva et al 2012], Poecilanthe Benth.
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